Transcript for Role of a Lifetime, Leading Lady Sally Field on Role in 'Lincoln'

With the oscars just a week away, the oscar-nominated sally field revealing what was playing behind the camera as she was portraying mrs. Lincoln in front of them. Here's abc's chris connelly. Reporter: Sally field has been a beloved part of american culture for nearly a half-century. Well, I learned my lesson. FROM HER '60s SITCOM "GIDGET," The flying nun. AND "FORREST GUMP" IN THE '90s. I'm home, mama. I know. Reporter: Today, at 66, she has as many best actress academy awards as meryl streep does, still she was undaunted and unabashed to play mary todd lincoln. Alongside daniel day-lewis in steven spielberg's "lincoln." Madam president, if you please. Reporter: In this acclaimed performance for which she poured through books for the former first lady, gained 25 pounds, nearly didn't happen. Because mary was ten years younger than lincoln, it wasn't going to work. Reporter: But spielberg decided to give her one more chance. A customarily reclusive daniel day-lewis offered to fly in for the day to act with her. When he walked across the room, I said mr. Lincoln, and he kissed the top of my head and said, my honor. And it will be one of the things that I remember forever and ever and ever. Reporter: For field, there's much to be proud of, three sons, four grandkids. Her performance achieved under more challenging circunces than she has previously shared. My mom passed away while i was doing "lincoln." She was very ill. So it was ongoing. Reporter: Margaret field herself was an actress. It was like her gift. You know, it was a gift. It's just was very, very hard. But, it was the way it was supposed to be.

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